U.S. patent number 5,616,632 [Application Number 08/560,586] was granted by the patent office on 1997-04-01 for silicone compositions.
This patent grant is currently assigned to Shin-Etsu Chemical Co., Ltd.. Invention is credited to Hironao Fujiki, Takashi Kondou, Shigeki Shudo.
United States Patent |
5,616,632 |
Fujiki , et al. |
April 1, 1997 |
Silicone compositions
Abstract
In a silicone composition comprising an aliphatic unsaturated
group-containing diorganopolysiloxane and an
organohydrogenpolysiloxane, there is blended a hydrosilylation
catalyst. The catalyst is obtained by stabilizing a platinum group
compound with an organopolysiloxane of formula (3): wherein R.sup.4
is a C.sub.2-8 aliphatic unsaturated group, R.sup.5 is a monovalent
hydrocarbon group excluding an aliphatic unsaturated group and
methyl group, letters f, g, and h are (f+g)/(f+g+h).gtoreq.0.10,
0.0001<f.ltoreq.2.0, and 1.8<f+g+h<2.205. The stabilized
platinum group compound is included in a silicone resin comprising
at least a R.sup.6 SiO.sub.3/2 or SiO.sub.4/2 unit wherein R.sup.6
is a monovalent hydrocarbon group, at least 10 mol % of the organic
groups being the same group as R.sup.5, the silicone resin having a
melting or softening point of 30.degree. to 200.degree. C. The
composition has improved shelf stability and curing properties.
Inventors: |
Fujiki; Hironao (Usui-gun,
JP), Shudo; Shigeki (Usui-gun, JP), Kondou;
Takashi (Usui-gun, JP) |
Assignee: |
Shin-Etsu Chemical Co., Ltd.
(Tokyo, JP)
|
Family
ID: |
26457272 |
Appl.
No.: |
08/560,586 |
Filed: |
November 20, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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436582 |
May 8, 1995 |
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Foreign Application Priority Data
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May 9, 1994 [JP] |
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6-119580 |
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Current U.S.
Class: |
523/211; 523/212;
525/478; 528/15 |
Current CPC
Class: |
C08K
9/10 (20130101); C08L 83/04 (20130101); C08K
9/10 (20130101); C08L 83/04 (20130101); C08L
83/04 (20130101); C08G 77/12 (20130101); C08G
77/20 (20130101); C08G 77/24 (20130101); C08G
77/70 (20130101); C08L 83/00 (20130101); C08L
2666/52 (20130101) |
Current International
Class: |
C08K
9/10 (20060101); C08K 9/00 (20060101); C08L
83/00 (20060101); C08L 83/04 (20060101); C08K
009/10 () |
Field of
Search: |
;528/15 ;525/478
;523/211,212 |
References Cited
[Referenced By]
U.S. Patent Documents
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3419593 |
December 1968 |
Willing et al. |
5254656 |
October 1993 |
Bilgrien et al. |
5373078 |
December 1994 |
Juen et al. |
|
Primary Examiner: Marquis; Melvyn I.
Attorney, Agent or Firm: Millen, White, Zelano &
Branigan, P.C.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of application Ser. No.
08/436,582 filed on May 8, 1995, now abandoned, the entire contents
of which are hereby incorporated by reference.
Claims
We claim:
1. A silicone composition comprising, in admixture,
(A) a diorganopolysiloxane of the general formula (1):
wherein R.sup.1 is an aliphatic unsaturated group having 2 to 8
carbon atoms, R.sup.2 is a substituted-or unsubstituted monovalent
hydrocarbon group excluding an aliphatic unsaturated group and
methyl group, letters a, b, and c are numbers in the range:
c/(a+b+c).gtoreq.0.95, 0.0001<a<0.05, and 1.8
<a+b+c<2.205, said diorganopolysiloxane containing at least
two aliphatic unsaturated groups in a molecule, at least 95 mol %
of the organic groups bonded to silicon atoms exclusive of a
silicon-oxygen bond being methyl,
(B) an organohydrogenpolysiloxane of the general formula (2):
wherein R.sup.3 is an substituted or unsubstituted monovalent
hydrocarbon group, letters d and e are numbers in the range:
0.002.ltoreq.e.ltoreq.1.0, 0.8.ltoreq.s d <2.2, and
0.8<d+e.ltoreq.3.0, having at least three hydrogen atoms each
bonded to a silicon atom in a molecule, and
(C) a hydrosilylation catalyst in the form of a platinum group
compound stabilized by coordination with an organopolysiloxane of
the general formula (3):
wherein R.sup.4 is an aliphatic unsaturated group having 2 to 8
carbon atoms, R.sup.5 is a substituted or unsubstituted monovalent
hydrocarbon group excluding an aliphatic unsaturated group and
methyl group, letters f, g, and h are numbers in the range:
(f+g)/(f+g+h).gtoreq.0.10, 0.0001<f.ltoreq.2.0, and
1.8<f+g+h<2.205, said organopolysiloxane containing at least
two aliphatic unsaturated groups in a molecule, at least 10 mol %
of the organic groups bonded to silicon atoms exclusive of a
silicon-oxygen bond being a group other than methyl,
said stabilized platinum group compound being included in a
silicone resin comprising at least one kind of units selected from
the group consisting of R.sup.6 SiO.sub.3/2 and SiO.sub.4/2 units,
and optionally further comprising R.sup.6.sub.3 SiO.sub.1/2 and/or
R.sup.6.sub.2 SiO.sub.2/2 units wherein R.sup.6 is a substituted or
unsubstituted monovalent hydrocarbon group, at least 10 mol % of
the organic groups bonded to silicon atoms exclusive of a
silicon-oxygen bond being the same group as R.sup.5 in formula (3),
said silicone resin having a melting or softening point of
30.degree. to 200.degree. C.
2. The silicone composition of claim 1 wherein the
organohydrogenpolysiloxane is present in an amount such that the
amount of the hydrogen atom bonded to a silicon atom in formula (2)
is 0.4 to 10 equivalents per aliphatic unsaturated group contained
in the entire composition.
3. The silicone composition of claim 1 wherein the silicone resin
contains 0 to 30 mol % of R.sup.6.sub.3 SiO.sub.1/2 unit, 0 to 30
mol % of R.sup.6.sub.2 SiO.sub.2/2 unit and 70 to 100 mol % of
R.sup.6 SiO.sub.3/2 unit wherein R.sup.6 is as described above.
4. The silicone composition of claim 1 wherein the silicone resin
contains 0 to 50 mol % of R.sup.6.sub.3 SiO.sub.1/2 unit, 0 to 30
mol % of R.sup.6.sub.2 SiO.sub.2/2 unit, 0 to 70 mol % of R.sup.6
SiO.sub.3/2 unit and 30 to 80 mol % of SiO.sub.4/2 unit wherein
R.sup.6 is as described above.
5. The silicone composition of claim 1 wherein the compound
occupies about 80 to 99.9% by weight of the entire hydrosilylation
catalyst.
6. The silicone composition of claim 1 wherein the hydrosilylation
catalyst is present in such an amount as to provide about 1 to
about 2,000 parts by weight of platinum group metal atom per
million parts by weight of the entire composition.
7. The silicone composition of claim 1, wherein, in formula (1),
the R.sup.1 groups are independently a vinyl, allyl, propenyl or
butenyl group, and the R.sup.2 groups are independently an ethyl,
propyl, butyl, phenyl or tolyl group wherein some or all of the
hydrogen atoms are optionally replaced by halogen atoms.
8. The silicone composition of claim 1, wherein the
diorganopolysiloxane of formula (1) has a viscosity of 50 to
10,000,000 cp at 25.degree. C.
9. The silicone composition of claim 1, wherein, in formula (2),
the R.sup.3 groups are independently a substituted or unsubstituted
monovalent hydrocarbon group of 1-12 carbon atoms.
10. The silicone composition of claim 1, wherein, in formula (2),
the R.sup.3 groups are independently a vinyl, allyl, propenyl,
butenyl, methyl, ethyl, propyl, butyl, phenyl or tolyl group
wherein some or all of the hydrogen atoms are optionally replaced
by halogen atoms.
11. The silicone composition of claim 1, wherein the
organohydrogenpolysiloxane of formula (2) has a viscosity of 1 to
500 cp at 25.degree. C.
12. The silicone composition of claim 1, wherein the platinum group
compound is a platinum-containing compound.
13. The silicone composition of claim 1, wherein, in formula (3),
the R.sup.4 groups are independently a vinyl, allyl, propenyl,
butenyl, ethynyl or propargyl group and the R.sup.5 groups are
independently an ethyl, propyl, butyl, phenyl or tolyl group
wherein some or all of the hydrogen atoms are optionally replaced
by halogen atoms.
14. The silicone composition of claim 1, wherein the
organopolysiloxane of formula (3) has a viscosity of 1 to 5,000,000
cp at 25.degree. C.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a silicone composition of the addition
curing type and more particularly, to such a silicone composition
which is shelf stable at room temperature, quickly curable upon
heating, and applicable in a variety of fields as potting agents,
adhesives, and coating agents and in extrusion molding and liquid
injection molding systems.
2. Prior Art
On heating, silicone compositions of the addition curing type are
curable through hydrosilylation reaction in the presence of
platinum compound catalysts. They are used in a multiplicity of
applications because of the advantages that the curing reaction
completes within a very short time and entails no by-products.
Undesirably, these silicone compositions are unstable during shelf
storage at room temperature. One countermeasure is to divide the
composition into two parts for storage and combine them together on
use, but it is unacceptable for practical use.
To overcome this drawback, a number of compounds capable of
controlling a hydrosilylation reaction have been proposed. For
example, U.S. Pat. No. 3,188,300 discloses organic phosphorus
compounds, U.S. Pat. No. 3,445,420 or JP-B 31476/1969 discloses
acetylene alcohols, U.S. Pat. No. 3,882,083 or JP-B 41626/1980
discloses triallylisocyanurates, U.S. Pat. No. 4,061,609 or JP-B
20340/1982 discloses hydroperoxides, U.S. Pat. No. 3,699,073 or
JP-B 10947/1973 and U.S. Pat. No. 3,923,705 or JP-B 56563/1988
disclose high vinyl siloxanes. Silicone compositions having such
control agents added thereto offer a sufficient pot life and
curability as long as the compositions are used by conventional
techniques. In the current market, more severe requirements are
imposed on silicone compositions, that is, more satisfactory shelf
stability and quick curing characteristics are required.
Encapsulation techniques are known to satisfy such requirements. In
JP-B 41707/1978, a protected catalyst powder is prepared by mixing
a platinum catalyst with a silicone resin having a melting point of
40.degree. to 200.degree. C. and pulverizing or spray drying the
mixture. U.S. Pat. No. 4,481,341 or JP-A 37053/1983, U.S. Pat. No.
4,784,879 or JP-A 47442/1989 and 45468/1989 disclose a platinum
catalyst encapsulated with a thermoplastic resin. The former
technique cannot fully improve the shelf stability of silicone
compositions. The latter technique of microcapsulation with organic
resin is successful in enhancing the shelf stability of silicone
compositions, but not in providing quick curing characteristics as
required in the current market.
Therefore, there is a need to have a technique capable of further
improving the shelf stability and curing characteristics of
addition curing type silicone compositions.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a silicone
composition of the addition curing type which has satisfactory
shelf stability and improved curing characteristics and is quickly
curable upon heating.
According to the present invention, there is provided a silicone
composition comprising, in admixture, (A) a diorganopolysiloxane,
(B) an organohydrogenpolysiloxane, and (C) a hydrosilylation
catalyst.
The diorganopolysiloxane (A) is of the general formula (1):
wherein R.sup.1 is an aliphatic unsaturated group having 2 to 8
carbon atoms, R.sup.2 is a substituted or unsubstituted monovalent
hydrocarbon group excluding an aliphatic unsaturated group and
methyl group, letters a, b, and c are numbers in the range:
c/(a+b+c).gtoreq.0.95, 0.0001<a<0.05, and
1.8<a+b+c<2.205. The diorganopolysiloxane contains at least
two aliphatic unsaturated groups in a molecule. At least 95 mol %
of the organic groups bonded to silicon atoms (exclusive of a
silicon-oxygen bond) is methyl.
The organohydrogenpolysiloxane (B) is of the general formula
(2):
wherein R.sup.3 is a substituted or unsubstituted monovalent
hydrocarbon group, letters d and e are numbers in the range:
0.002.ltoreq.e.ltoreq.1.0, 0.8.ltoreq.d<2.2, and
0.8<d+e.ltoreq.3.0. The organohydrogenpolysiloxane has at least
three hydrogen atoms each bonded to a silicon atom in a
molecule.
The hydrosilylation catalyst (C) is in the form of a platinum group
compound stabilized by coordination with an organopolysiloxane of
the general formula (3):
wherein R.sup.4 is an aliphatic unsaturated group having 2 to 8
carbon atoms, R.sup.5 is a substituted or unsubstituted monovalent
hydrocarbon group excluding an aliphatic unsaturated group and
methyl group, letters f, g, and h are numbers in the range:
(f+g)/(f+g+h).gtoreq.0.10, 0.0001<f.ltoreq.2.0, and
1.8<f+g+h<2.205. The organopolysiloxane contains at least two
aliphatic unsaturated groups in a molecule. At least 10 molt of the
organic groups bonded to silicon atoms (exclusive of a
silicon-oxygen bond) is a group other than methyl. The stabilized
platinum group compound is included or enclosed in a silicone resin
comprising at least one kind of unit selected from the group
consisting of R.sup.6 SiO.sub.3/2 and SiO.sub.4/2 units, and
optionally further comprising R.sup.6.sub.3 SiO.sub.1/2 and/or
R.sup.6.sub.2 SiO.sub.2/2 units wherein R.sup.6 is a substituted or
unsubstituted monovalent hydrocarbon group. At least 10 mol % of
the organic groups bonded to silicon atoms (exclusive of a
silicon-oxygen bond) is the same group as R.sup.5 in formula (3).
The silicone resin has a melting or softening point of 30.degree.
C. to 200.degree. C.
By blending diorganopolysiloxane (A), organohydrogenpolysiloxane
(B), and hydrosilylation catalyst (C), there is obtained a silicone
composition of the addition curing type which remains unchanged in
quality after long-term storage at room temperature (for example,
10.degree. C. to 30.degree. C.), need not be divided into two or
more parts for shelf storage. That is, the composition has
satisfactory shelf stability. Upon heating, the composition is
quickly curable into cured products having satisfactory physical
properties. These physical properties change little depending on
environmental conditions during storage covering from room
temperature to elevated temperature.
More particularly, in the silicone composition of the invention,
the aliphatic unsaturated group-bearing organopolysiloxane of
formula (3) is coordinated to the platinum group compound for
stabilizing and fixing the platinum group compound to form a
siloxane complex of the platinum group compound. This stabilized
platinum group compound is included or incorporated in the silicone
resin defined above which is essentially incompatible with the
diorganopolysiloxane of formula (1) at room temperature (for
example, 10.degree. C. to 30.degree. C.), but compatible with the
organopolysiloxane of formula (3) owing to their similarity in
structure. The resin embedment allows the platinum group compound
as a hydrosilylation catalyst to be kept outside the reaction
system under storage conditions. Heating causes the platinum group
compound to diffuse uniformly in the system for promoting
hydrosilylation reaction. Since the present invention is
characterized in that the platinum group compound is made
compatible and integral with the enclosing silicone resin during
storage, it is apparently distinguishable from the catalyst powder
having platinum catalyst protected with silicone resin described in
JP-B 41707/1978 and the containment of platinum element in
micro-capsules described in U.S. Pat. No. 4,481,341 and JP-A
5063/1993. This difference, quite surprisingly, contributes to
significantly superior long-term shelf stability and quick curing
properties as compared with the conventional encapsulation
techniques.
Moreover, the silicone composition of the invention eliminates the
drawback of the conventional microcapsulation techniques that once
heated above the melting point, the composition becomes short in
shelf life. Even when the composition has physically experienced
high shear forces during manufacture, its capability is not
impaired at all. The drawback that shelf stability is
instantaneously or gradually lost is also eliminated.
BEST MODE FOR CARRYING OUT THE INVENTION
A first essential component (A) of the silicone composition of the
present invention is an organopolysiloxane which is selected from
well-known organopolysiloxanes commonly used as the main component
of conventional addition curing type silicone rubber compositions.
More particularly, it is a diorganopolysiloxane of the general
formula (1).
wherein R.sup.1 is an aliphatic unsaturated group having 2 to 8
carbon atoms, R.sup.2 is a substituted or unsubstituted monovalent
hydrocarbon group excluding an aliphatic unsaturated group and
methyl group, letters a, b, and c are numbers in the range:
c/(a+b+c).gtoreq.0.95, 0.0001<a<0.05, and
1.8<a+b+c<2.205. The diorganopolysiloxane contains at least
two aliphatic unsaturated groups in a molecule. At least 95 mol %
of the organic groups bonded to silicon atoms (exclusive of a
silicon-oxygen bond) is methyl.
More particularly, R.sup.1 is an aliphatic unsaturated group having
2 to 8 carbon atoms, for example, alkenyl group such as vinyl,
allyl, propenyl, and butenyl groups, with alkenyl groups such as
vinyl being most preferred. R.sup.2 is a substituted or
unsubstituted monovalent hydrocarbon group excluding an aliphatic
unsaturated group and methyl group, preferably having 2 to 12
carbon atoms, for example, alkyl groups exclusive of methyl such as
ethyl, propyl and butyl, aryl groups such as phenyl and tolyl, and
substituted ones of these groups wherein all or some of the
hydrogen atoms are substituted by halogen atoms or the like, such
as 3,3,3-trifluoropropyl, C.sub.4 F.sub.9 CH.sub.2 CH.sub.2 --,
C.sub.8 F.sub.17 CH.sub.2 CH.sub.2 --, and perfluoroalkyl ether
groups. Letters a, b, and c are numbers satisfying
c/(a+b+c).gtoreq.0.95, 0.0001<a<0.05, and
1.8<a+b+c<2,205.
The diorganopolysiloxane of formula (1) should contain at least two
aliphatic unsaturated groups preferably having 2 to 8 carbon atoms,
typically at least two alkenyl groups as R.sup.1 in a molecule. At
least 95 mol % of the organic groups bonded to silicon atoms
(exclusive of a silicon-oxygen bond), that is, based on 100 mol %
of R.sup.1, R.sup.2 and CH.sub.3 in formula (1) combined, should be
methyl.
The diorganopolysiloxane of formula (1) may be either a linear one
or a branched one partially containing an RSiO.sub.3/2 or
SiO.sub.4/2 unit wherein R is a substituted or unsubstituted
monovalent hydrocarbon group. Preferably it has a viscosity of
about 50 to 10,000,000 centipoise (cp) at 25.degree. C. A
diorganopolysiloxane with a viscosity of less than 50 cp would be
too brittle to provide silicone rubber elasticity. A
diorganopolysiloxane with a viscosity of more than 10,000,000 cp
would be unsuitable for blending as rubber.
The diorganopolysiloxane of formula (1) can be synthesized by any
well-known method, for example, by effecting equilibration reaction
between an organocyclopolysiloxane and a hexaorganodisiloxane in
the presence of an alkali or acid catalyst.
A second essential component (B) of the silicone composition
according to the invention is an organohydrogenpolysiloxane which
serves as a crosslinking agent by reacting with
diorganopolysiloxane (A). It is of the general formula (2):
wherein R.sup.3 is a substituted or unsubstituted monovalent
hydrocarbon group, letters d and e are numbers in the range:
0.002.ltoreq.e.ltoreq.1.0, 0.8.ltoreq.d<2.2, and
0.8<d+e.ltoreq.3.0. It has at least three hydrogen atoms each
bonded to a silicon atom in a molecule.
In formula (2), R.sup.3 is preferably a substituted or
unsubstituted monovalent hydrocarbon group having 1 to 12 carbon
atoms, for example, aliphatic unsaturated groups such as vinyl,
allyl, propenyl and butenyl, alkyl groups such as methyl, ethyl,
propyl and butyl, aryl groups such as phenyl and tolyl, and
substituted ones of these groups wherein all or some of the
hydrogen atoms are substituted by halogen atoms or the like, such
as 3,3,3-trifluoropropyl, C.sub.4 F.sub.9 CH.sub.2 CH.sub.2 --,
C.sub.8 F.sub.17 CH.sub.2 CH.sub.2 --, and perfluoroalkyl ether
groups. Letters d and e are numbers satisfying
0.002.ltoreq.e.ltoreq.1.0, 0.8.ltoreq.d<2.2, and
0.8<d+e.ltoreq.3.0. Preferably 0.01.ltoreq.e<1.0,
1.5<d.ltoreq.2.0, and 1.6d+e<2.8.
The organohydrogenpolysiloxane of formula (2) should have at least
three hydrogen atoms each bonded to a silicon atom in a
molecule.
No particular limit is imposed on the molecular structure of the
organohydrogenpolysiloxane of formula (2). It may be either of
linear, cyclic and branched structures. Preferably it has a
viscosity of about 1 to 500 cp at 25.degree. C.
The organohydrogenpolysiloxane of formula (2) can be readily
synthesized by any well-known method, for example, by effecting
equilibration reaction of octamethylcyclotetrasiloxane,
tetramethylcyclotetrasiloxane, and a compound containing
hexamethyldisiloxane or
1,1'-dihydro-2,2',3,3'-tetramethyldisiloxane to become a terminal
group in the presence of a catalyst such as sulfuric acid,
trifluoromethanesulfonic acid, and methanesulfonic acid at a
temperature of about -10.degree. C. to about +40.degree. C.
In the practice of the invention, organohydrogenpolysiloxane (B) is
preferably blended so that the amount of the hydrogen atom bonded
to a silicon atom in formula (2) is 0.4 to 10 equivalents,
especially 0.8 to 5 equivalents per aliphatic unsaturated group
contained in the entire composition. Less than 0.4 equivalent of
hydrogen atom on this basis would lead to a too low crosslinking
density, sometimes adversely affecting the heat resistance of
silicone rubber. With more than 10 equivalents of hydrogen atom, a
bubbling problem would result from dehydrogenation reaction and
heat resistance would be exacerbated.
A third essential component (C) of the silicone composition
according to the present invention is a hydrosilylation catalyst in
the form of a platinum group compound which is stabilized by
coordination with an organopolysiloxane and further included in a
silicone resin. The organopolysiloxane used herein is of the
general formula (3):
wherein R.sup.4 is an aliphatic unsaturated group having 2 to 8
carbon atoms, R.sup.5 is a substituted or unsubstituted monovalent
hydrocarbon group excluding an aliphatic unsaturated group and
methyl group, letters f, g, and h are numbers in the range:
(f+g)/(f+g+h).gtoreq.0.10, 0.0001<f.ltoreq.2.0, and
1.8<f+g+h+2.205. The organopolysiloxane of formula (3) contains
at least two aliphatic unsaturated groups in a molecule. At least
10 mol %, preferably 10 to 95 mol %, more preferably 30 to 95 mol %
of the organic groups bonded to silicon atoms (exclusive of a
silicon-oxygen bond), that is, based on 100 mol % of R.sup.4,
R.sup.5, and CH.sub.3 in formula (3) combined, is a group other
than methyl. The silicone resin in which the stabilized platinum
group compound is included is a silicone resin comprising at least
one kind of unit selected from the group consisting of R.sup.6
SiO.sub.3/2 and SiO.sub.4/2 units, and optionally further
comprising R.sup.6.sub.3 SiO.sub.1/2 and/or R.sup.6.sub.2
SiO.sub.2/2 units wherein R.sup.6 is a substituted or unsubstituted
monovalent hydrocarbon group. At least 10 mol % of the organic
groups bonded to silicon atoms (exclusive of a silicon--oxygen
bond) is the same group as R.sup.5 in formula (3). The silicone
resin has a melting or softening point of 30.degree. to 200.degree.
C.
This hydrosilylation catalyst promotes hydrosilylation reaction
between diorganopolysiloxane (A) and organohydrogenpolysiloxane (B)
to produce a crosslinked structure in the silicone composition so
that the composition may be used as an elastomer after curing.
Any of compounds of platinum, rhodium, ruthenium and palladium may
be used as the platinum group compound. Platinum compounds are
preferred from the standpoints of economy and ability. Exemplary
platinum compounds are commonly used ones such as chloroplatinic
acid, complexes thereof with alcohols, and complexes thereof with
vinylsiloxanes such as divinyltetramethyldisiloxane, and
1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane
In the organopolysiloxane of formula (3) with which the platinum
compound is stabilized by coordination, R.sup.4 is an aliphatic
unsaturated group having 2 to 8 carbon atoms, for example, alkenyl
groups such as vinyl, allyl, propenyl, and butenyl and alkynyl
groups such as ethynyl and propargyl, with the alkenyl groups,
typically vinyl being preferred. R.sup.5 is a substituted or
unsubstituted monovalent hydrocarbon group excluding an aliphatic
unsaturated group and methyl group, preferably having 2 to 12
carbon atoms, for example, alkyl groups exclusive of methyl such as
ethyl, propyl, and butyl, aryl groups such as phenyl and tolyl, and
substituted ones of these groups wherein all or some of the
hydrogen atoms are substituted by halogen atoms or the like, such
as 3,3,3-trifluoropropyl, C.sub.4 F.sub.9 CH.sub.2 CH.sub.2 --,
C.sub.8 F.sub.17 CH.sub.2 CH.sub.2 --, and perfluoroalkyl ether
groups, with the phenyl and fluorinated hydrocarbon groups being
preferred. Letters f, g, and h are numbers satisfying
(f+g)/(f+g+h).gtoreq.0.10, 0.0001<f.ltoreq.2.0, and
1.8<f+g+h<2,205.
The organopolysiloxane of formula (3) should contain at least two
aliphatic unsaturated groups in a molecule. At least 10 mol % of
the organic groups bonded to silicon atoms (exclusive of a
silicon-oxygen bond) is a group other than methyl. Preferably the
organopolysiloxane of formula (3) is substantially insoluble or
sparingly soluble in diorganopolysiloxane (A) at room temperature
(for example, 0.degree. to 30.degree. C.). Preferably the
organopolysiloxane of formula (3) has a viscosity of about 1 to
5,000,000 cp at 25.degree. C., especially 100 to 1,000,000 cp at
25.degree. C. and a degree of siloxane polymerization of up to
about 1,000.
Examples of the organopolysiloxane of formula (3) include high
vinyl content organopolysiloxanes described in U.S. Pat. No.
3,699,073 corresponding to JP-B 10947/1973 as well as compounds of
the following structures. ##STR1##
R: methyl, vinyl, phenyl or trifluoropropyl
Stabilization by coordination of the platinum group compound may be
accomplished by forming a siloxane complex of the platinum group
compound, for example, by directly reacting chloroplatinic acid
with an organopolysiloxane of formula (3) followed by
neutralization with sodium hydrogen carbonate, or by ripening an
alcohol or vinylsiloxane complex of chloroplatinic acid together
with an organopolysiloxane of formula (3).
The organopolysiloxane of formula (3) may be used in amounts such
that the alkenyl group in the organopolysiloxane is present in an
amount of at least 2 moles, preferably 2 to 80 moles, more
preferably 5 to 20 moles per one mole of the platinum group metal.
If the molar ratio is less than 2, the stabilization of the
platinum group compound by coordination may not be fully attained.
If the molar ratio is more than 80, the catalytic activity of the
platinum group may be lowered.
The silicone resin in which the stabilized platinum group compound
is included is a silicone resin comprising at least a R.sup.6
SiO.sub.3/2 or SiO.sub.4/2 unit among R.sup.6.sub.3 SiO.sub.1/2,
R.sup.6.sub.2 SiO.sub.2/2, R.sup.6 SiO.sub.3/2, and SiO.sub.4/2
units. At least 10 mol % of the organic groups bonded to silicon
atoms exclusive of a silicon-oxygen bond is the same group as
R.sup.5 in formula (3). The silicone resin has a melting or
softening point of 30.degree. to 200.degree. C. This silicone resin
is generally compatible with the stabilized platinum group
compound, but incompatible with diorganopolysiloxane (A) under
normal temperature (e.g., 10.degree. C. to 30.degree. C.).
Preferably, the silicone resin contains 0 to 30 mol % of
R.sup.6.sub.3 SiO.sub.1/2 unit, 0 to 30 mol % of R.sup.6.sub.2
SiO.sub.2/2 unit and 70 to 100 mol % of R.sup.6 SiO.sub.3/2 unit in
the absence of SiO.sub.4/2 unit, or contains 0 to 50 mol % of
R.sup.6 SiO.sub.3/2 unit, 0 to 30 mol % of R.sup.6.sub.2
SiO.sub.2/2 unit, 0 to 70 mol % of R.sup.6 SiO.sub.3/2 unit and 30
to 80 mol % of SiO.sub.4/2 unit.
R.sup.6 is a substituted or unsubstituted monovalent hydrocarbon
group, for example, those groups exemplified for R.sup.3 in formula
(2).
In the silicone resin, at least 10 mol % of the entire organic
groups bonded to silicon atoms is the same group as R.sup.5 in
formula (3), with phenyl and fluorinated groups being most
desirable.
The silicone resin has a melting or softening point of 30.degree.
to 200.degree. C., especially 40.degree. C. to 150.degree. C. A
silicone resin with a melting or softening point of lower than
30.degree. C. permits the catalyst component to bleed out,
detracting from shelf stability. A silicone resin with a melting or
softening point of higher than 200.degree. C. will not effectively
and quickly melt or soften upon heat curing of the composition,
prohibiting effective utilization of the catalyst component.
Preferred examples of the silicone resin are phenyl-containing
silicone resins and fluorinated silicone resins as described in
JP-A 5063/1993 and U.S. Pat. No. 5,232,959 or JP-A 36354/1992. It
is to be noted that these prior art techniques also use
platinum-vinylsiloxane complexes similar to those used in the
present invention. The present invention is different from the
prior art techniques in that the siloxane forming the
platinum-siloxane complex has a structure analogous to the silicone
resin enclosing the platinum-siloxane complex so that these two are
compatible and integratable. Owing to this feature, the silicone
composition is surprisingly improved in shelf stability.
The stabilized platinum compound is included in the silicone resin,
for example, by mixing the two components in an organic solvent
such as dichloromethane, benzene, methyltrichlorosilane, and
dioxane and spray drying or freeze drying the solution. In this
regard, the mixing ratio between the stabilized platinum compound
and the enclosing silicone resin is preferably such that the
resulting hydrosilylation catalyst may have a softening point of
30.degree. to 200.degree. C. Generally the enclosing silicone resin
occupies about 80 to 99.9% by weight of the entire hydrosilylation
catalyst.
In the composition of the invention, the hydrosilylation catalyst
is preferably added in such an amount as to provide about 1 to
about 2,000 parts, more preferably about 5 to about 1,000 parts by
weight of platinum group metal atom per million parts by weight of
the entire composition. Less than 1 ppm would fail to provide the
composition with a satisfactory curing rate. More than 2,000 ppm
would be economically disadvantageous and can detract from shelf
stability.
In the silicone composition of the invention, an adhesive component
may be additionally blended in order to impart adhesive ability.
The adhesive component used herein includes those compounds
commercially available as carbon functional silanes, such as
vinyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane,
3-methacryloxypropyltrimethoxysilane,
3-glycidoxypropyltrimethoxysilane, and
2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and compounds having
a hydrogen atom, alkenyl, alkoxy or epoxy group directly bonded to
a silicon atom in a molecule, as exemplified below. ##STR2##
Preferably the adhesive component is added in amounts of 0 to 20
parts per 100 parts by weight of diorganopolysiloxane (A).
Where it is desired to impart strength to the composition of the
invention, finely divided silica having a specific gravity of 50
m.sup.2 /g or more is added. Examples of the finely divided silica
include Aerosil 130, 200 and 300 (Nihon Aerosil K. K. and Degussa
Inc.), Cabosil MS-5 and MS-7 (Cabot Corp.), Rheorosil QS-102 and
QS-103 (Tokuyama Soda K. K.), and Nipsil LP (Nihon Silica K. K.) as
hydrophilic silica; and Aerosil R-812, R-812S, R-972 and R-974
(Degussa Inc.), Rheorosil MT-10 (Tokuyama Soda K. K.), and Nipsil
SS series (Nihon Silica K. K.) as hydrophobic silica. Preferably 0
to 30 parts by weight of the finely divided silica is added per 100
parts by weight of diorganopolysiloxane (A).
In the practice of the invention, the silicone composition may
further contain therein other components, for example,
semi-reinforcing fillers such as ground quartz, diatomaceous earth,
calcium carbonate, alumina and carbon black; inorganic pigments
such as cobalt blue; coloring agents such as organic dyes; agents
for enhancing heat resistance and flame resistance such as cerium
oxide, zinc carbonate, manganese carbonate, iron oxide and titanium
oxide. These components may be added in conventional amounts
insofar as the effect of the present invention is not impaired.
EXAMPLE
Examples of the present invention are given below by way of
illustration and not by way of limitation. All parts are by
weight.
Synthetic Example 1
Preparation of Platinum Compound
A flask with a stirrer was charged with 4 g of chloroplatinic acid,
15 g of an organopolysiloxane compound of the structure shown below
(7.1 moles of vinyl group in the organopolysiloxane per one mole of
platinum metal), and 100 g of methyl isobutyl ketone and then with
2.6 g of sodium hydrogen carbonate. The contents were stirred for
one hour at room temperature, heated to 80.degree. C., and stirred
for a further 4 hours at the temperature. ##STR3##
Next, the solution was concentrated at 80.degree. C. in a vacuum of
10 mmHg, obtaining a vinylphenylsiloxane complex of chloroplatinic
acid (designated platinum compound A, platinum concentration 1%
).
Preparation of Phenylsiloxane Resin
A flask with a stirrer was charged with 148 g of
phenyltrichlorosilane and 53 g of propyltrichlorosilane, which were
subject to hydrolysis. Then 5 g of hexamethyldisilane was added to
the flask. The contents were stirred for 2 hours at 70.degree. C.,
effecting silylation. The volatiles were distilled off in vacuum,
yielding phenylsiloxane resin having a softening point of
83.degree. C. and 0.1 mol % of Si-OH group (designated silicone
resin A).
Preparation of Hydrosilylation Catalyst
In 100 g of dichloromethane were dissolved 30 g of platinum
compound A and 30 g of silicone resin A. The solution was spray
dried, obtaining 17 g of a hydrosilylation reaction catalyst having
the platinum compound enclosed in the silicone resin (designated
catalyst 1).
Synthetic Example 2
In 100 g of benzene were dissolved 30 g of platinum compound A and
30 g of silicone resin A (both prepared in Synthetic Example 1).
The solution was solidified with dry ice/methanol, allowed to warm
up to room temperature in vacuum, and kept in vacuum until the
solvent distilled off. This freeze drying technique yielded 28 g of
a hydrosilylation reaction catalyst having the platinum compound
enclosed in the silicone resin (designated catalyst 2).
Synthetic Example 3
Synthesis of 3,3,3-trifluoropropyl-Containing Vinylsiloxane Oil
In a flask equipped with a dropping funnel, reflux condenser, and
stirrer, 15 g of a cyclic siloxane trimer of
3,3,3-trifluoropropyltrimethylcyclotrisiloxane was dissolved in 200
g of tetrahydrofuran. To the solution 1,000 g of magnesium vinyl
bromide was added dropwise. Distilled water was added to the
reaction solution, which was heated at 60.degree. C. and stirred
for 3 hours.
The reaction solution was concentrated at 100.degree. C. under a
vacuum of 10 mmHg. The concentrate was poured into a mixture of 10%
aqueous hydrochloric acid and toluene in a molar ratio of 1:1,
heated at 60.degree. C. and stirred for 20 hours. Thereafter, the
solution was washed with water and dried over sodium sulfate,
obtaining a 3,3,3-trifluoropropyl group-containing vinylsiloxane
oil of the following structure. ##STR4##
Preparation of Platinum Compound
A flask with a stirrer was charged with 4 g of chloroplatinic acid,
12 g of the 3,3,3-trifluoropropyl-containing vinylsiloxane oil (7.0
moles of vinyl group in the vinylsiloxane oil per 1 mole of
platinum metal), and 100 g of methanol and then with 2.6 g of
sodium hydrogen carbonate. The contents were stirred for one hour
at room temperature, heated to 80.degree. C., and stirred for a
further 4 hours at the temperature.
Next, the solution was concentrated at 60.degree. C. in a vacuum of
10 mmHg, obtaining a 3,3,3-trifluoropropyl-containing vinylsiloxane
complex of chloroplatinic acid (designated platinum compound B,
platinum concentration 1%).
Preparation of Fluorinated Siloxane Resin
A flask with a stirrer was charged with 185 g of
trifluoropropyltrichlorosilane and 30 g of methyltrichlorosilane,
which were subject to hydrolysis. Then 5 g of hexamethyldisilane
was added to the flask. The contents were stirred for 2 hours at
70.degree. C., effecting silylation. The volatiles were distilled
off in vacuum, yielding a fluorinated siloxane resin having a
softening point of 86.degree. C. and 0.2 mol % of Si-OH group
(designated silicone resin B).
Preparation of Hydrosilylation Catalyst
In 150 g of dioxane were uniformly dissolved 30 g of platinum
compound B and 30 g of silicone resin B. The solution was freeze
dried, obtaining 16 g of a hydrosilylation reaction catalyst having
the platinum compound enclosed in the silicone resin (designated
catalyst 3).
Synthetic Example 4
Synthesis of Vinyl-Containing 3,3,3-trifluoropropylsiloxane Long
Chain Oil
In a flask equipped with a dropping funnel, reflux condenser, and
stirrer, 22 g of a cyclic siloxane trimer of
methylvinylcyclotrisiloxane was dissolved in 63 g of acetonitrile.
A catalytic amount of a penta-coordinated silicon catalyst of the
formula shown below and distilled water were added to the solution,
which was stirred for 4 hours. ##STR5##
The solution was then cooled to 10.degree. C., in which 200 g of a
cyclic siloxane trimer of
3,3,3-trifluoropropyltrimethylcyclotrisiloxane and a catalytic
amount of the pentacoordinated silicon catalyst were dissolved and
stirred for 6 hours.
Further, 20.4 g of dimethylvinylchlorosilane and 35 g of
pentamethyldivinyldisilazane were added to the solution, which was
heated at 100.degree. C. and stirred for one hour. Thereafter, the
solution was concentrated at 150.degree. C. in a vacuum of 20 mmHg.
The concentrate was allowed to cool down to room temperature and
filtered under pressure, obtaining a vinyl-containing
3,3,3-trifluoropropylsiloxane long chain oil of the following
structure. ##STR6##
Preparation of Platinum Compound
A flask with a stirrer was charged with 10 g of a toluene solution
of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum complex
(platinum concentration 5%), 90 g of the vinyl-containing
3,3,3-trifluoropropylsiloxane long chain oil (63 moles of vinyl
group in the long chain oil per mole of platinum metal), and 200 g
of methyl isobutyl ketone. The contents were heated to 80.degree.
C. and stirred for 4 hours.
Next, the solution was concentrated at 80.degree. C. in a vacuum of
10 mmHg, obtaining a vinyl-containing 3,3,3-trifluoropropyl long
chain siloxane platinum complex (designated platinum compound C,
platinum concentration 1%).
Preparation of Hydrosilylation Catalyst In 150 g of dioxane were
uniformly dissolved 30 g of platinum compound C and 30 g of
silicone resin B. The solution was freeze dried, obtaining 17 g of
a hydrosilylation reaction catalyst having the platinum compound
enclosed in the silicone resin (designated catalyst 4).
Synthetic Example 5
Preparation of Platinum Compound
A flask with a stirrer was charged with 4 g of chloroplatinic acid,
6.4 g of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (7.0 moles of
vinyl group in the disiloxane per 1 mole of platinum metal), and
100 g of ethanol and then with 2.6 g of sodium hydrogen carbonate.
The contents were stirred for one hour at room temperature, heated
to 80.degree. C., and stirred for a further 4 hours at the
temperature.
Next, the solution was concentrated at 80.degree. C. in a vacuum of
10 mmHg, obtaining a vinylmethylsiloxane complex of chloroplatinic
acid (designated platinum compound D, platinum concentration
0.5%).
Preparation of Hydrosilylation Catalyst
In 150 g of dichloromethane were dissolved 30 g of platinum
compound D and 30 g of silicone resin A (prepared in Synthetic
Example 1). The solution was spray dried, obtaining 16 g of a
hydrosilylation reaction catalyst having the platinum compound
enclosed in the silicone resin (designated catalyst 5).
Synthetic Example 6
Preparation of hydrosilylation catalyst
In 150 g of dioxane were dissolved 30 g of platinum compound D
(prepared in Synthetic Example 5) and 30 g of silicone resin B
(prepared in Synthetic Example 3). The solution was freeze dried,
obtaining 16 g of a hydrosilylation reaction catalyst having the
platinum compound enclosed in the silicone resin (designated
catalyst 6).
Example 1
A kneader was charged with 100 parts of a dimethylsiloxane polymer
blocked with a dimethylvinylsilyl group at either end and having a
viscosity of 10,000 centipoise (cp) at 25.degree. C., 20 parts of
fumed silica having a specific surface area of 300 m.sup.2 /g, 8
parts of hexamethyldisilazane, and 1 part of water. The contents
were agitated and kneaded for one hour at room temperature, heated
to 150.degree. C., and kneaded for a further 2 hours at the
temperature. The mixture was then cooled down to room temperature.
To the mixture were added 20 parts of a dimethylsiloxane polymer
blocked with a dimethylvinylsilyl group at either end and having a
viscosity of 10,000 cp at 25.degree. C. and 3 parts of
hydrogenmethylpolysiloxane of the following formula having a
viscosity of about 10 cp at 25.degree. C. They were uniformly
mixed. ##STR7##
To 100 parts of the mixture were added 1 part of
1,5-dihydrogen-1,3,5,7-tetramethyl-3-trimethoxysilylethyl-7-glycidylpropyl
tetrasiloxane and 0.2 part of triallylisocyanurate. They were
uniformly mixed, obtaining a silicone rubber base compound.
To 100 parts of the silicone rubber base compound was added 0.5
part of catalyst 1 obtained in Synthetic Example 1. They were
uniformly mixed, obtaining a curable silicone composition.
Example 2
A curable silicone composition was prepared as in Example 1 except
that 0.5 part of catalyst 2 obtained in Synthetic Example 2 was
added instead of catalyst 1.
Example 3
To 100 parts of the silicone rubber base compound prepared in
Example 1 was added 0.5 part of catalyst 3 obtained in Synthetic
Example 3. They were uniformly mixed and further uniformly milled
in a three-roll mill, obtaining a curable silicone composition.
Example 4
To 100 parts of the silicone rubber base compound prepared in
Example 1 was added 0.5 part of catalyst 4 obtained in Synthetic
Example 4. They were uniformly mixed, obtaining a curable silicone
composition.
Comparative Example 1
To 100 parts of the silicone rubber base compound prepared in
Example 1 was added 1 part of catalyst 5obtained in Synthetic
Example 5. They were uniformly mixed, obtaining a curable silicone
composition. Comparative Example 2
To 100 parts of the silicone rubber base compound prepared in
Example 1 was added 1 part of catalyst 6 obtained in Synthetic
Example 6. They were uniformly mixed, obtaining a curable silicone
composition.
These curable silicone compositions of Examples 1-4 and Comparative
Examples 1-2 were examined for curing properties and shelf
stability. The results are shown in Table 1.
Curing Upon Heating.
A silicone composition was heated at 120.degree. C. for curing.
Using a curelastmeter, the time (IT) taken until curing of the
composition initiated and the time (T90) taken until the torque
reached 90% of the maximum were determined as measures of
curability.
Shelf Stability
A silicone composition was allowed to stand at 40.degree. C. and
the time taken until the composition lost fluidity was determined
as a pot life.
TABLE 1 ______________________________________ Comparative Example
Example 1 2 3 4 1 2 ______________________________________ Curing
properties IT (sec.) 30 31 31 32 30 22 T90 (sec.) 90 95 100 1000 90
84 Shelf stability 7 7 10 12 3 3 Pot life (day)
______________________________________
As is evident from Table 1, the compositions within the scope of
the invention (Examples 1 to 4) have good curing behavior and
improved shelf stability.
There has been described a silicone composition which has improved
shelf stability in that it is stable at room temperature over a
long time and acceptable curing properties in that it is quickly
curable upon heating, and which accommodates the recent
requirements in the market. The composition is applicable in a
variety of fields as potting agents, adhesives, and coating agents
and in extrusion molding and liquid injection molding systems.
Japanese Patent Application No. 119580/1994 is incorporated herein
by reference.
Although some preferred embodiments have been described, many
modifications and variations may be made thereto in the light of
the above teachings. It is therefore to be understood that within
the scope of the appended claims, the invention may be practiced
otherwise than as specifically described.
* * * * *